U.S. Pat. No. 4,806,893 entitled "Molded Case Circuit Breaker Actuator-Accessory Unit" describes the use of an electromagnetic actuator within an actuator-accessory unit to articulate a circuit breaker operating mechanism to separate the circuit breaker contacts upon the occurrence of an overcurrent condition of predetermined magnitude. An electronic trip unit in combination with current transformers are used within so-called "electronic trip" circuit breakers to sense the circuit current and determine when such a tripping function should be inputted to the actuator-accessory unit. The electronic trip unit and actuator-accessory unit replace prior art thermally and magnetically active trip elements which respond to changing circuit current in an analog fashion.
The operating mechanism and latch assembly used within the electronic trip circuit breakers are described in U.S. Pat. No. 4,736,174 entitled "Molded Case Circuit Breaker Operating Mechanism" and U.S. Pat. No. 4,864,263 entitled "Molded Case Circuit Breaker Latch and Operating Mechanism Assembly". The latch assembly within the operating mechanism is found within U.S. Pat. No. 4,789,848 and the cradle operator used within the operating mechanism is found within U.S. Pat. No. 5,059,933.
It has been determined that when the circuit breaker operating mechanism is articulated from a remote location by use of a motor operator, such as that described within U.S. Pat. No. 3,171,920 whereby a mechanical force is applied to the circuit breaker handle operator, the force transmitted to the operating mechanism is far in excess of that required for articulating the operating mechanism and substantially increases the rate at which the operating mechanism responds to drive the circuit breaker contacts between their ON-OFF conditions. The increased response rate could, in turn, adversely affect the life of the components within those operating mechanisms designed mainly for manual operation at a much slower response rate.
Accordingly, one purpose of the invention is to provide a circuit breaker operating mechanism that is capable of responding to the increased operating rates required with remote operating devices without affecting the life of the operating mechanism components absorbing huge impact forces without damage without substantial alteration to the existing operating mechanism design.